Even a tire iron, one of my best friends had one under her car seat - she even had a name for the blasted thing. " Sleepy time" Haha.
Also, trust your instincts. Usually they are right on. If something feels weird or not right, it's not.
Another thing, rings. Even the big, gaudy fake ones. Turn it around so that the large part is inside your palm. One good slap with that and you can get away..